Common electronic documents can be classified into fixed-layout documents and flow-layout documents based on different display modes thereof. Fixed-layout documents utilize an absolute positioning mode to record the location and the size of each primitive such that the documents are scalable as a whole in accordance with various display screen sizes using a consistent typesetting format (i.e. the layout, the font or the like are entirely consistent with those of the corresponding paper documents). Therefore, fixed-layout documents have the same display effects as the corresponding paper documents. In contrast, flow-layout documents only record the size of each primitive and the sequential relationship between the primitives, and thus various display formats are available based on different screen sizes. Hence, the line feeds between paragraphs and the word sizes are adjustable according to the width of display screens.
Fixed-layout documents can be classified into the following two kinds of documents:
1) those from which data content cannot be extracted, such as scanned documents; and
2) those from which data content can be extracted, such as PDF (Portable Document Format) documents. For this kind of documents, the data contents can be reformatted according to the storage order thereof without considering their absolute positioning.
In addition to the above fixed-layout and flow-layout documents, there is another kind of document named as fixed-flow-layout documents. Fixed-flow-layout documents record not only the absolute location and the size of each primitive but also the sequential relationship between the primitives. Therefore, fixed-flow-layout documents can be displayed using both the fixed-layout mode and the flow-layout mode.
Accordingly, fixed-flow-layout documents and fixed-layout documents from which data content can be extracted (such as PDF documents) can be displayed using the fixed-layout mode or the flow-layout mode. Nowadays, fixed-flow-layout documents are generally displayed in fixed-layout by default on large screens (such as the screen of an office computer), and in flow-layout by default on screens of mobile equipment (such as the screen of a mobile phone). However, with the development of electronic equipment, their screen sizes have become highly diversified; for example, the screens of tablet PCs have become smaller and smaller, while those of mobile phones have become wider and wider. Therefore, it may be unreliable to select display modes based on equipment types, and unable to achieve optimal display effects using conventional default display methods.